PAR lamps are typically comprised of a light source such as a tungsten halogen capsule or a high intensity discharge (HID) arc tube mounted within a glass body in conjunction with a parabolic reflector. The glass body can be pressed borosilicate glass. A lens usually covers the front or light-emitting end of the body and can contain optical elements to provide a desired beam shape (for example, a spot or flood beam). General service PAR lamps usually have a neck region between the parabolic reflector and the base, and the base generally comprises a threaded fitting for connecting the lamp to a power source via a socket. The usual power source is 100 to 240 volts. The neck provides the mechanical support between the reflector optical portion and the base electrical portion. The neck additionally provides room for the capsule press seal, the lead-ins, capsule mounting components, and wiring and separates the light source (i.e., the filament or arc discharge) from the base to reduce the base temperature. Additionally, when the light source is an arc discharge source, the neck area can also contain the appropriate integral ballast for the arc discharge light source. It is with the latter type of PAR lamp that this invention pertains.
Integrally ballasted HID PAR lamps generate considerable heat which must be appropriately handled for the lamp to operate properly and, in addition to the visible light they provide, often emit undesired electromagnetic interference (EMI). Such EMI can have unwanted side effects and its reduction is a very desired feature.
In the prior art, such reduction has been accomplished by applying shielding between a light and a complementary module (U.S. Pat. No. 6,916,204 B2) or by connecting the reflective coating on a reflector to system ground whereby extraneous radio frequency emissions are shielded by the reflector (U.S. Pat. No. 5,993,034).
Such techniques have been difficult to accomplish in integrally ballasted PAR lamps, which also require critical alignment of the components and special techniques for fabricating the reflectors.